全文获取类型
收费全文 | 6170篇 |
免费 | 415篇 |
国内免费 | 4篇 |
出版年
2022年 | 32篇 |
2021年 | 64篇 |
2020年 | 18篇 |
2019年 | 43篇 |
2018年 | 64篇 |
2017年 | 64篇 |
2016年 | 91篇 |
2015年 | 150篇 |
2014年 | 177篇 |
2013年 | 326篇 |
2012年 | 306篇 |
2011年 | 313篇 |
2010年 | 192篇 |
2009年 | 185篇 |
2008年 | 317篇 |
2007年 | 290篇 |
2006年 | 336篇 |
2005年 | 301篇 |
2004年 | 334篇 |
2003年 | 284篇 |
2002年 | 270篇 |
2001年 | 203篇 |
2000年 | 182篇 |
1999年 | 190篇 |
1998年 | 84篇 |
1997年 | 95篇 |
1996年 | 59篇 |
1995年 | 72篇 |
1994年 | 80篇 |
1993年 | 64篇 |
1992年 | 118篇 |
1991年 | 112篇 |
1990年 | 105篇 |
1989年 | 85篇 |
1988年 | 79篇 |
1987年 | 68篇 |
1986年 | 100篇 |
1985年 | 86篇 |
1984年 | 95篇 |
1983年 | 69篇 |
1982年 | 55篇 |
1981年 | 47篇 |
1980年 | 36篇 |
1979年 | 52篇 |
1978年 | 41篇 |
1977年 | 36篇 |
1976年 | 35篇 |
1975年 | 19篇 |
1974年 | 28篇 |
1973年 | 24篇 |
排序方式: 共有6589条查询结果,搜索用时 31 毫秒
971.
972.
973.
974.
975.
976.
The effect of photosynthetically active radiation and temperature on the photosynthesis of two Vietnamese species of Sargassum,S. mcclurei and S. oligocystum,based on the field and laboratory measurements
下载免费PDF全文
![点击此处可从《Phycological Research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ryuta Terada Triet D. Vo Gregory N. Nishihara Kazuya Matsumoto Shogo Kokubu Yuki Watanabe Shigeo Kawaguchi 《Phycological Research》2016,64(4):230-240
SUMMARY The effects of photosynthetically active radiation (PAR) and temperature on the photosynthesis of two Vietnamese brown algae, Sargassum mcclurei and S. oligocystum (Fucales), were determined by field and laboratory measurements. Dissolved oxygen sensors and pulse‐amplitude modulated (PAM) fluorometry were used for the measurements of photosynthetic efficiency. A Diving‐PAM revealed that underwater measurements of the effective quantum yield (Φ PSII ) of both species declined with increasing incident PAR, with minimum Φ PSII occurring during noon to early afternoon. Φ PSII recovered in the evening, indicating photo‐adaptation to excessive PAR. In laboratory experiments, Φ PSII also decreased under continuous exposure to 1000 μmol photons m?2 s?1; and full recovery occurred after 12 h of dark acclimatization. The net photosynthesis – PAR experiments of S. mcclurei and S. oligocystum conducted at 28°C revealed that the net photosynthetic rate quickly increased at PAR below the saturation irradiance of 361 and 301 μmol photons m?2 s?1 and nearly saturated to maximum net photosynthetic rates of 385 and 292 μg O2 gww ? 1 min?1 without photoinhibition, respectively. Gross photosynthesis and dark respiration experiments determined over a range of temperatures (12–40°C), revealed that the maximum gross photosynthetic rates of 201 and 147 μg O2 gww ? 1 min?1 occurred at 32.9 and 30.7°C for S. mcclurei and S. oligocystum, respectively. The dark respiration rates increased exponentially over the temperature ranges examined. The estimated maximum value of the maximum quantum yield occurred at 19.3 and 20.0°C and was 0.76 and 0.74, respectively. Similar to the natural habitat of the study site, these two species tolerated the relatively high temperatures and broad range of PAR. The ability of these species to recover from exposure to high PAR is one of the mechanisms that allow them to flourish in the shallow water environment. 相似文献
977.
978.
Endo N Nishiyama K Okabe M Matsumoto M Kanouchi H Oka T 《Biochimica et biophysica acta》2007,1770(4):571-577
Hyperhomocysteinemia is an important risk factor for atherosclerosis. We previously reported that formation of early atherosclerosis in the rat aorta was associated with hyperhomocysteinemia and reduction of antioxidant activity caused by low concentration of vitamin B(6)in vivo. In the present study, we examined effects of vitamin B(6) on apoptosis of bovine endothelial cells (NM-1 cells) treated with homocysteine and copper. Homocysteine and copper induced extracellular hydrogen peroxide, intracellular ROS and cellular lipid peroxide levels. Cell viability was reduced to 30% compared to that of control cells. On the other hand, pyridoxal treatment as well as EDTA treatment increased viability of NM-1 cells treated with homocysteine and copper to about 60%, and significantly decreased extracellular hydrogen peroxide, intracellular ROS and cellular lipid peroxide levels. The treatment of catalase recovered cell viability and reduced the level of extracellular hydrogen peroxide and intracellular ROS. Cell death by homocysteine and copper was confirmed to be due to apoptosis by evaluation of DNA fragmentation and by TUNEL assay. However, apoptosis of NM-1 cells induced by homocysteine and copper was due to a caspase-independent pathway as it was not inhibited by the caspase inhibitor, Z-VAD-fmk. Apoptosis of NM-1 cells induced by homocysteine and copper accompanied with mitochondrial permeability but not cytochrome c release. These results suggest that pyridoxal treatment suppresses apoptosis of NM-1 cells induced by homocysteine and copper, most likely through antioxidant effects. 相似文献
979.
Ono M Maya Y Haratake M Ito K Mori H Nakayama M 《Biochemical and biophysical research communications》2007,361(1):116-121
A novel series of aurone derivatives for in vivo imaging of beta-amyloid plaques in the brain of Alzheimer's disease (AD) were synthesized and characterized. When in vitro binding studies using Abeta(1-42) aggregates were carried out with aurone derivatives, they showed high binding affinities for Abeta(1-42) aggregates at the K(i) values ranging from 1.2 to 6.8 nM. When in vitro plaque labeling was carried out using double transgenic mice brain sections, the aurone derivatives intensely stained beta-amyiloid plaques. Biodistribution studies in normal mice after i.v. injection of the radioiodinated aurones displayed high brain uptake (1.9-4.6% ID/g at 2 min) and rapid clearance from the brain (0.11-0.26% ID/g at 60 min), which is highly desirable for amyloid imaging agents. The results in this study suggest that novel radiolabeled aurones may be useful amyloid imaging agents for detecting beta-amyloid plaques in the brain of AD. 相似文献